1. Technical Field
The present invention generally relates to communication systems, such as cellular communication networks, and particularly relates to a method and system for statistically reusing resources, such as spreading codes or carrier tones, in communication systems.
2. Background
Current and developing wireless communication systems commonly employ transmit link adaptation, which varies one or more data transmission parameters in response to changing reception conditions. As one example, a remote receiver evaluates received signal quality, determines the received data rate it can support at that quality, and returns a corresponding data rate request to the originating transmitter. In response, the transmitter uses the requested data rate to adjust its next transmission to the receiver.
Implicit in such systems is the notion that the receiver's reception conditions during the time interval in which the transmitter uses the adapted data rate are the same (or close enough) to the reception conditions existent when the receiver made its signal quality determination. However, at least some current (and many developing network standards) provide high-speed packet data services in which packet data incoming to the network for delivery to remote receivers generally has a random arrival distribution. That is, for some transmit intervals, some network transmitters have little or no data to send, while others have large amounts of data to send.
Thus, the individual transmission activities for packet data within a given group of network transmitters may vary widely over successive transmission intervals. Compounding these activity variations, there is a tendency for given network transmitters to allocate significant transmit power and/or other transmit resources if there is packet data to send in any given interval, as a basis for sending data at the highest achievable rate within that interval. With that approach, the interference caused by a transmitter with respect to receivers operating in surrounding areas can vary dramatically over successive transmit intervals, as a function of whether the transmitter has packet data to send, and, if so, as a function of the transmit resource allocations made by the transmitter for sending that data.
To appreciate the challenges such circumstances present to receivers trying to determine link adaptation feedback, consider that a given receiver may compute received signal quality at a time instant where one (or more) nearby transmitters are actively sending packet data, meaning that the receiver's signal quality calculation reflects the potentially high levels of interference caused by the nearby, active transmitters. Thus, to the extent that those nearby transmitters are inactive (or otherwise transmitting with lower interface) during a later reception time, the level of interference experienced by the receiver will be lower and its previously calculated signal quality will be overly pessimistic for those conditions. Consequently, the receiver will be underserved during the low interference condition, to the extent that the receiver's supporting transmitter has adapted its transmission link to the receiver based on the previously calculated signal quality.